Reinforced concrete is a mainstay in the construction of buildings, bridges, and other structures. Although other reinforcement methods exist, post-tensioning has been used in a number of applications. In basic terms, post-tensioning generally involves tensioning of long strands (sometimes referred to in the art as “tendons”) after a concrete slab has been poured and set.
It is a fairly common occurrence for the post-tension strands to be severed or otherwise damaged. As the strands are sometimes located relatively close to the surface of a slab, it is not uncommon for a strand to be inadvertently severed, for example, by cutting or sawing into a concrete slab during the course of other repair work, running service lines, etc. A severed strand can mean that the concrete slab is more vulnerable to failure such as cracking or sagging, which in the worst case could mean failure of the entire structure.
Repairing severed or damaged post-tension strands typically is a highly-complex, difficult and time intensive operation. To repair severed strands, a large section of the concrete slab must be first jack-hammered to form an opening exposing significant lengths of the broken ends of a strand. An additional strand section is coupled to one of the broken strands, and then the end of the additional strand section and the end of the other broken strand are fed through at least one bowtie anchor. Tension is then applied at each end of the bowtie anchor.
Current methods for repairing post-tension strands are undesirable for a number of reasons. For example, during the re-tensioning operation, care must be taken to limit the position and amount the bowtie coupler and/or strand twists so as to avoid protrusion of the bowtie coupler and/or strand above the surface of the concrete slab. If the bowtie coupler and/or strand ends up protruding above the surface of the concrete slab, resurfacing of the slab may be difficult and/or may produce inferior results.
Additionally, a relatively large area and depth of the concrete slab must be opened up to give the post-tension jacks enough surface against which to press while tensioning the strands. Moreover, in some situations, the concrete slab must be further reinforced to withstand the pressure encountered during the tensioning operation. These steps result in additional time, cost, and difficulty of the repair operation.